In search stopwords filtering, suppress possible PHP warnings when PCRE lacks UTF-8 support.

see #25709.

Built from https://develop.svn.wordpress.org/trunk@25932


git-svn-id: http://core.svn.wordpress.org/trunk@25891 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/query.php

@@ -1987,7 +1987,7 @@ class WP_Query {
 				$term = trim( $term, "\"' " );
 
 			// \p{L} matches a single letter that is not a Chinese, Japanese, etc. char
-			if ( ! $term || preg_match( '/^\p{L}$/u', $term ) )
+			if ( ! $term || @preg_match( '/^\p{L}$/u', $term ) )
 				continue;
 
 			if ( in_array( call_user_func( $strtolower, $term ), $stopwords, true ) )